The present invention relates to a means for detecting the contact wear of electrical devices having current-interrupting contacts, for example high voltage circuit-breakers, on-load tap changers, etc.
Because of the arc which normally arises between current-interrupting contacts, a certain amount of wear of these contacts occurs. The contacts must therefore be inspected and possibly replaced according to a scheme fixed for each contact device. The intervals between the inspections may be based on operating time or the number of performed operations, or a combination thereof. Usually, therefore, it is presupposed that all operations are carried out at a certain current. In most cases, this presupposition does not correspond to reality. Many operations are carried out at low current or in a currentless state, whereas other operations, due to special operating conditions or faulty functioning of the apparatus, may lead to severe loads on the contacts. Therefore, with predetermined, fixed service intervals many expensive shutdowns and inspections will be carried out without cause, while at the same time there is a risk of damage to apparatus due to worn contacts.